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A very important issue relating to the quality of a DAC is its power supply. Even a household washing machine has a power supply filter of some sort. Most DAC or CD player manufacturers incorporate a similar or slightly better approach to power supply filtering. Then there are the few who go to the extreme in the "capacitance race". The results are costly, but are they the best possible?

LessLoss, in our goal of achieving the best possible solution, has experimented extensively with the most radical power supply filtering methods. The result of this is a realization of the fact that a real-time power supply filter can never approach the quality attained by the filtering of power using the chemical means of rechargeable batteries, except in the digital realm.

Battery Power Supply

It is widely known that wide spectrum frequency interference causes intermodulation distortion in any audio amplification system. Purifying the power voltage from this wide frequency spectrum 'trash' is the goal of the power supply filter. However, in doing so, it also must not bottleneck the current flow to the amplification circuit. Excessive use of capacitance is the traditional solution to this problem. Other extreme solutions include running multiple transformers in series. These are highly costly and impractical solutions. Even when using battery power, some electromagnetic induction of high frequency interference occurs. However, as the amount is small, it is effectively filtered via the use of a small value capacitor.

Advantages of Battery Power

A battery is a source of direct current voltage. Using the alternating current of the city mains means not only rectifying the current using a diode bridge, but also filtering it using a large capacity electrolytic capacitor and voltage stabilizer. Even then some amount of undesirable pulsation enters the schematics, and these pulsations include a vast array of harmonics all the way up to the mid-audio bandwidth (about 1 kHz).

A side-effect of diode bridge rectifiers constantly turning on/off is that this results in undesirable switching interference of a rather wide spectrum. (For this reason there are all sorts of solutions such as "soft recovery" diodes which aim to lessen this problem.)

A diode within a diode bridge bears similarity to a diode detector in a radio receiver which turns radio frequency broadcast material into audio signals. If the DAC is to be used near a strong radio signal source, then that parasitic signal can enter the DAC's schematic.

Relay Circuit

The LessLoss DAC 2004 uses a multiple relay circuit to charge the batteries from the city mains while the device is not in use. When the user presses the Play button, the relays switch the mains power to the charging schematic off. The relays totally galvanically isolate the audio schematic, including the ground. This frees the DAC 2004 audio schematic from any and all influence resulting from mains interference. This could include your microwave oven, your CD player, or even your local radio station.

The digital section, on the other hand, actually benefits from wisely filtered mains power. In earlier designs, we did incorporate a separate battery for the digital section, but as our newly developed mains filtering solution clearly outperforms any battery solution for digital schematics, we have since abandoned the use of battery power for the digital section. Thus, the DAC 2004 presently employs a hybrid power supply based on a highly filtered mains power supply for the digital section and a balanced battery power supply for the analogue section.

Low Frequency Performance on Batteries?

It is often feared that low frequency performance is hampered by the use of battery power. This is probably due to widespread faulty circuit topology, but certainly not due to the batteries themselves. The DAC 2004 includes two separate batteries. They provide balanced power to the analogue schematics. These are the requirements for the best starting conditions for the cleanest operation of the audio signal schematics.

25x the Theoretically Necessary Current

The fully Class A battery power supply is constantly supported by 25 times the theoretically necessary current. This results in an operational time between battery charges of approximately 10 hours. When the batteries are low, the onboard automatic battery charger circuit automatically applies a trickle charge to the batteries. You can listen to music non-stop with no interruption to playback. When you want, you can press the Charge button and have the unit mute playback and charge the batteries overnight when you are no longer listening.

By pressing the Play button, the user may choose at any time to prematurely interrupt the charging process and commence playing before the batteries are fully charged. An adequate trickle charge remains, ensuring that the unit never cuts off the music.

Best Possible Performance Over Time

The charger begins charging the batteries before they run down. This prolongs their life and guarantees the same level of performance from them throughout their lifetime. Indeed, many users completely forget that this is a (partly) battery-powered unit!